Pectoral Block Failure May Be Due to Incomplete Coverage of Anatomical Targets: A Dissection Study.

BACKGROUND AND OBJECTIVES: The popularization of ultrasound-guided nerve blocks in cosmetic and reconstructive breast surgery calls for better anatomical understanding of chest wall innervation. When inserting subpectoral implants, pain from pocket dissection, stretching of muscle, and release of costal attachments may be relieved by blocking the pectoral nerves in the interpectoral (IP) space.We describe the variable anatomy of the pectoral nerves in the IP space in order to define the area to be covered for sufficient blockade, based on cadaver dissections. METHODS: Twenty-six fresh cadavers were dissected bilaterally. The number, location, and course of the pectoral nerves were recorded. Distances to surface landmarks (sternum, clavicle, and costae) and ultrasound landmarks (thoracoacromial artery [TAA] and pectoralis minor muscle [Pm]) were recorded. RESULTS: The lateral pectoral nerve and the TAA entered together into the IP space 8.9 cm (range, 8.0-12.0 cm) lateral to the midsternal line. The medial pectoral nerve (MPN) had between 1 and 4 branches that pierced the Pm, and 69% had additional branches lateral to the Pm. The muscle-piercing MPN branches were located 3.8 cm (range, 0.4-8.1 cm) and the lateral MPN branches 5.4 cm (range, 3.0-8.4 cm) from the lateral pectoral nerve. The IP course was 2.6 cm (range, 0.7-6.5 cm). All specimens were asymmetrical in location or number of MPN branches. CONCLUSIONS: The MPN branches that innervate the lower part of the pectoralis major muscle are asymmetrical and variable in location and length; all located in a triangular area easily defined by sonographic landmarks, lateral to the TAA.

Symptomatic Thoracic Nerve Root Herniation into an Extradural Arachnoid Cyst: Case Report and Review of the Literature.

BACKGROUND: Spinal extradural arachnoid cysts (SEACs) are relatively rare and usually asymptomatic. They preferentially are situated in the thoracic extradural space and almost always dorsal. SEACs may present with back pain and/or cord compression symptoms. Needle aspiration, needle fenestration, or open surgical resection/fenestration have been reported as treatment modalities. CASE DESCRIPTION: We present a 35-year-old woman who complained of radiating pain from the right lower thoracic region of her back toward the right inguinal region, which was aggravated upon defecation and straining. Magnetic resonance imaging (MRI) revealed an extradural cyst located laterally at T11-T12 level on the right, with a nerve root herniation. During a T11-T12 hemilaminectomy, on resection of the cyst wall, a nerve root was noted to be herniating into the cyst cavity through a dural defect. The nerve root was released and repositioned intradurally, followed by direct suture of the dural tear. Histologic findings of the cyst wall confirmed an arachnoid cyst. Postoperative course was uneventful without complications. Postoperative MRI confirmed a complete resection of the cyst. Five years after surgery, the patient is asymptomatic with complete recovery. CONCLUSIONS: Thoracic SEACs can present with radiating pain due to a transdural herniation of a thoracic nerve root into the cyst, potentially due to a mechanism of intermittent pressure gradients between the intradural and extradural spaces. MRI can prove beneficial in visualizing the nerve prolapsing into the cyst. Open resection of the cyst wall, reduction of the nerve root herniation, and subsequent direct closure of the dural tear led to complete recovery.

Minimal Access Posterior Approach for Extrapleural Thoracic Sympathectomy: A Cadaveric Study and Cases.

OBJECTIVE: Operatively, video-assisted thoracoscopic sympathectomy (VATS) involves pleural entry and poses risk in small children and patients with pulmonary disease. A conventional posterior sympathectomy is more invasive than VATS. We investigated a cadaveric feasibility study of a minimal access posterior approach for endoscopic extrapleural sympathectomy and discuss this minimal approach in children with cardiac sympathectomy. METHODS: A posterior endoscopic extrapleural approach for thoracic sympathectomy was performed using lightly embalmed cadavers; surgical corridor depth, width, and associated pleural violation were recorded. Two pediatric cases undergoing secondary prevention for breakthrough cardiac dysrhythmias using this approach are discussed: case 1, a 9-year-old girl with refractory long QT syndrome; and case 2, a 13-year-old boy with hypertrophic cardiomyopathy. RESULTS: The cadaveric study supported 100% identification of a craniocaudal-oriented sympathetic chain using an 18-mm tubular retractor, and a 10% pleural violation rate. There were no clinically significant pneumothoracies in either proof of concept cases. CONCLUSIONS: Minimal access posterior extrapleural sympathectomy is feasible to expose the sympathetic chain in the thoracic region with good visualization using either endoscopic or microscopic magnification. Single-position bilateral thoracic sympathectomy can be performed in pediatric patients with life-threatening ventricular arrhythmias. Based on the cadaveric study and the 2 preliminary cases, we believe that a posterior minimal access approach allows safe and effective access to the thoracic sympathetic chain for causes requiring sympathectomy using single positioning, with minimal risk of pneumothorax or Horner syndrome.

Octopamine stabilizes conduction reliability of an unmyelinated axon during hypoxic stress.

Mechanisms that could mitigate the effects of hypoxia on neuronal signaling are incompletely understood. We show that axonal performance of a locust visual interneuron varied depending on oxygen availability. To induce hypoxia, tracheae supplying the thoracic nervous system were surgically lesioned and action potentials in the axon of the descending contralateral movement detector (DCMD) neuron passing through this region were monitored extracellularly. The conduction velocity and fidelity of action potentials decreased throughout a 45-min experiment in hypoxic preparations, whereas conduction reliability remained constant when the tracheae were left intact. The reduction in conduction velocity was exacerbated for action potentials firing at high instantaneous frequencies. Bath application of octopamine mitigated the loss of conduction velocity and fidelity. Action potential conduction was more vulnerable in portions of the axon passing through the mesothoracic ganglion than in the connectives between ganglia, indicating that hypoxic modulation of the extracellular environment of the neuropil has an important role to play. In intact locusts, octopamine and its antagonist, epinastine, had effects on the entry to, and recovery from, anoxic coma consistent with octopamine increasing overall neural performance during hypoxia. These effects could have functional relevance for the animal during periods of environmental or activity-induced hypoxia.

Length-dependent axo-terminal degeneration at the neuromuscular synapses of type II muscle in SOD1 mice.

In motor neuron diseases, there is a prolonged period of time before any clinical symptoms begin to appear. During this time, distal axonal degeneration, or "dying back" axonopathy, begins to occur before the onset of clinical symptoms and motor neuron death. This preclinical degeneration is a hallmark of motor neuron diseases in both animal models and human patients. Generally, in muscles with mixed fiber types, distal degeneration occurs in fast-fatigable α-motor axons innervating type IIb muscle fibers before axons innervating slow, type I muscle fibers. We investigated whether the "dying back" axonopathy in a pure fast-fatigable α-motor axon nerve is a length-dependent process. The lateral thoracic nerve (LTN) exclusively consists of motor nerves that innervate the very thin cutaneous maximus muscle (CMM) that solely contains type II neuromuscular synapses. We characterized the LTN and CMM synapses both morphologically and physiologically in the superoxide dismutase 1 (SOD1) mutant mouse model of amyotrophic lateral sclerosis (ALS). By 60days of age, there was a significant "dying back" phenomenon at the caudal region while the rostral region remained intact. The longer axons innervating the caudal region appear to be more susceptible to degeneration in the SOD1 mouse indicating that the axonal degeneration of motor neurons innervating type II fibers is a length-dependent process. Additionally, we identified how the simplicity of the LTN-CMM system offers a better method to investigate axon degeneration in an ALS mouse model and may be used to investigate possible therapeutic compounds for axon protection and regeneration.

Maternal protein restriction increases respiratory and sympathetic activities and sensitizes peripheral chemoreflex in male rat offspring.

BACKGROUND: Maternal protein restriction in rats increases the risk of adult offspring arterial hypertension through unknown mechanisms. OBJECTIVES: The aims of the study were to evaluate the effects of a low-protein (LP) diet during pregnancy and lactation on baseline sympathetic and respiratory activities and peripheral chemoreflex sensitivity in the rat offspring. METHODS: Wistar rat dams were fed a control [normal-protein (NP); 17% protein] or an LP (8% protein) diet during pregnancy and lactation, and their male offspring were studied at 30 d of age. Direct measurements of baseline arterial blood pressure (ABP), heart rate (HR), and respiratory frequency (Rf) as well as peripheral chemoreflex activation (potassium cyanide: 0.04%) were recorded in pups while they were awake. In addition, recordings of the phrenic nerve (PN) and thoracic sympathetic nerve (tSN) activities were obtained from the in situ preparations. Hypoxia-inducible factor 1α (HIF-1α) expression was also evaluated in carotid bifurcation through a Western blotting assay. RESULTS: At 30 d of age, unanesthetized LP rats exhibited enhanced resting Rf (P = 0.001) and similar ABP and HR compared with the NP rats. Despite their similar baseline ABP values, LP rats exhibited augmented low-frequency variability (∼91%; P = 0.01). In addition, the unanesthetized LP rats showed enhanced pressor (P = 0.01) and tachypnoeic (P = 0.03) responses to peripheral chemoreflex activation. The LP rats displayed elevated baseline tSN activity (∼86%; P = 0.02) and PN burst frequency (45%; P = 0.01) and amplitude (53%; P = 0.001) as well as augmented sympathetic (P = 0.01) and phrenic (P = 0.04) excitatory responses to peripheral chemoreflex activation compared with the NP group. Furthermore, LP rats showed an increase of ∼100% in HIF-1α protein density in carotid bifurcation compared with NP rats. CONCLUSION: Sympathetic-respiratory overactivity and amplified peripheral chemoreceptor responses, potentially through HIF-1α-dependent mechanisms, precede the onset of hypertension in juvenile rats exposed to protein undernutrition during gestation and lactation.

Can Thoracic Sympathetic Nerve Damage Be Reversed?

BACKGROUND: Function of the thoracic sympathetic chain (TSC) reportedly recovers after surgical clips are removed. Hence, this study was designed to study nerve regeneration after unclipping the TSC. METHODS: The bilateral TSCs of six goats were studied; the goats were separated into three groups (groups I, II, and III) during excision, clipping, and unclipping. During surgery, the TSCs were excised with a scalpel in group I and clipped in groups II and III. In group III, the clips were removed 1 month postoperatively and observed for possible nerve healing for 1 month. All TSCs were examined histologically following en block resection at 1 month postoperatively in groups I and II and at 2 months postoperatively in group III. RESULTS: Inflammation in nerve sections was noted following clip removal. Furthermore, there was significant degeneration and cell infiltration in the nerve fibers of the clipped regions. The Schwann cells around the peripheral nerve endings in the unclipped regions facilitated nerve transmission by reconstitution of myelin. CONCLUSION: Clipping the TSC can cause histologic degeneration; however, histologic nerve regeneration occurs after unclipping.

Cord compression due to extradural thoracic nerve root hemangioblastoma.

Hemangioblastomas (HGBs) are benign tumors that occur sporadically or as part of von Hippel-Lindau (VHL) disease. 6-8% of spinal HGBs are extramedullary in location, and basically referred to as HGB of the spinal nerve root. Purely extradural (ED) location is the rarest form of these tumors. We report a case of a non-VHL patient with large thoracic ED HGB, who presented with myelopathy due to cord compression. We emphasize the importance of correct pre-operative diagnosis as well as pre-operative embolization in order to reach the goal of complete tumor resection with minimal complications. We also review the relevant literature and summarize the few case reports of this unique tumor.

Visualization of the Long Thoracic Nerve using High-Resolution Sonography.

PURPOSE: The long thoracic nerve (LTN) innervates the serratus anterior muscle (SA) which plays an important role in shoulder function. Evaluation of the LTN has so far been restricted to clinical assessment and partly electromyography and neurography. Progress of high-resolution ultrasound (HRUS) increasingly enables visualization of small peripheral nerves and their pathologies. We therefore aimed at (a) clarifying the possibility of visualization of the LTN from its origin to the most distal point in the supraclavicular region visible and (b) developing an ultrasound protocol for routine use. We further present two cases of patients with LTN pathology. METHODS: The study consisted of two parts: Part 1 included 4 non-enbalmed human bodies in whom the LTN (n = 8) was located and then marked by ink injection. Correct identification was confirmed by anatomical dissection. Part 2 included 20 healthy volunteers whose LTN (n = 40) was assessed independently by two radiologists. Identification of the LTN was defined as consensus in recorded images. RESULTS: LTN was clearly visible in all anatomical specimens and volunteers using HRUS and could be followed until the second slip of the serratus anterior muscle from the supraclavicular region. In anatomical specimens, dissection confirmed HRUS findings. For all volunteers, consensus was obtained. The mean nerve diameter was 1.6 mm ±â€Š0.3 (range 1.1 - 2.1 mm) after the formation of the main trunk. DISCUSSION: We hereby confirm a reliable possibility of visualization of the LTN in anatomical specimens as well as in volunteers. We encourage HRUS of the LTN to be part of the diagnostic work-up in patients presenting with scapular winging, shoulder weakness or pain of unknown origin.

Morphometric analysis of thoracic ganglion neurons in subjects with and without primary palmar hyperhidrosis.

BACKGROUND: Hyperhidrosis (HH) is a disease whose physiopathology remains poorly understood and that adversely affects quality of life. There is no morphologic study that includes an adequate control group that allows for comparison of the ganglion of HH to those of normal individuals. The purpose of study was to analyze morphologic and morphometric characteristics of the ganglion from patients with HH and normal individuals (organ donators). METHODS: This was a transversal study. The sympathetic thoracic ganglia were obtained from 2 groups of patients. Group PH (palmar hyperhidrosis), 40 patients with palmar HH submitted to surgery by video-assisted thoracoscopy, and group C (control group), 14 deceased individuals (control group of organ donators) without any history of HH. The third left sympathetic thoracic ganglion was resected in all patients. RESULTS: We observed higher number of cells in the PH group than in the control group (14.25 + 3.81 vs. 10.65 + 4.93) with P = 0.007; the mean percentage of ganglion cells stained by caspases-3 in the PH group was significantly greater than that of the C group (2.37 + 0.79 vs. 0.77 + 0.28) with P < 0.001; the mean value of area of collagen in the PH group was 0.80 IQ (0.08-1.87), and in the control group it was 2.36 IQ (0.49-5.98) with P = 0.061. CONCLUSIONS: Subjects with primary palmar HH have a higher number of ganglion cells within the ganglion and a higher number of cells in apoptosis. Also, the subjects of PH group have less collagen in the sympathetic ganglion when compared with the control group, but not statistically significant.

Thoracic nerve root hemangioblastoma: a rare cause of posterior mediastinal mass.

BACKGROUND: Hemangioblastomas are benign tumors that occur sporadically or as part of von Hippel-Lindau disease. Occasionally, they have an extramedullary location along the nerve roots and, rarely, are purely extradural. CASE DESCRIPTION: We report a rare case of a completely extradural large hemangioblastoma in a 32-year-old man presenting with radiculopathy and a posterior mediastinal mass. Screening revealed a similar tumor in the right cerebellar hemisphere. The patient underwent a right paramedian suboccipital craniotomy and total excision of the cerebellar tumor, followed by a left lateral thoracotomy and complete excision of the mediastinal lesion. The patient had an uneventful recovery. CONCLUSIONS: Hemangioblastomas should be considered in the diagnosis of posterior mediastinal tumors in the presence of typical imaging features or with associated intra-axial tumors, so as to plan preoperative angiography and embolization.

The effects of clipping on thoracic sympathetic nerve in rabbits: early and late histopathological findings.

BACKGROUND: The clipping of the thoracic sympathetic nerve, which has been a technique used for approximately the past 10 years, has rapidly become popular because of its "bring-back" claim. However, the information regarding the mechanism behind this claim is based on investigator's comments and has not been proven by objective research, such as the histopathological examination of the clipped nerve and/or ganglion. We aimed to evaluate sympathetic regeneration and degeneration after clip removal. METHODS: The rabbits were divided into two groups with six rabbits per group. For the first group (group A), the sympathetic chain was clipped using two titanium clips, and a right thoracotomy was made at the T4 and T5 levels. For the second group (group B), the animals were also operated on, which was similar to the rabbits in group A. At the end of a 48-hour follow-up period, the clips were removed after a second operation. The rabbits in group B were followed for 45 days and sympathetic nerves were also examined histopathologically. RESULTS: In group A, hemorrhage, fibrinous material, polymorphonuclear leukocyte infiltration, and acute inflammation with fat necrosis were observed in and around the sympathetic ganglia and trunk. Loss of nuclei and vacuolization in some sympathetic ganglia cells were also observed. These findings demonstrated severe degeneration of the sympathetic ganglia and trunk. For group B, microscopic examination revealed a loss of sympathetic ganglion cells as well as fibrosis within and around the ganglia. No signs of regeneration were detected and the progression of nerve degeneration was observed. CONCLUSIONS: The clips used in our study were shown to cause the degeneration of neural structures within 2 days. At the end of the 45 days following the removal of the clips, progressive, degenerative changes radiating along the axons of the sympathetic cells were seen.

Surgical anatomy of the pectoral nerves and the pectoral musculature.

The pectoral nerves (PNs) may be selectively injured through various traumatic mechanisms such as direct trauma, hypertrophic muscle compression, and iatrogenic injuries (breast surgery and axillary node dissection, pectoralis major muscle transfers). The PN may be surgically recovered through nerve transfers. They may also be used as donors to the musculocutaneous, axillary, long thoracic, and spinal accessory nerves and for reinnervation of myocutaneous free flaps. Thus, in this article, we reviewed the surgical anatomy of PN. A meta-analysis of the available literature showed that the lateral pectoral nerve (LPN) arises most frequently with two branches from the anterior divisions of the upper and middle trunks (33.8%) or as a single root from the lateral cord (23.4%). The medial pectoral nerve (MPN) usually arises from the medial cord (49.3%), anterior division of the lower trunk (43.8%), or lower trunk (4.7%). The two PN are usually connected immediately distal to the thoracoacromial artery by the so-called ansa pectoralis. The MPN may also show communications with the intercostobrachial nerve. In 50%-100% of cases, it may pass, at least with some branches, through the pectoralis minor muscle. The LPN supplies the upper portions of the pectoralis major muscle; the MPN innervates the lower parts of the pectoralis major and the pectoralis minor muscle. Among the accessory muscles of the pectoral girdle, the LPN may also innervate the tensor semivaginae articulationis humero-scapularis, pectoralis minimus, sternoclavicularis, axillary arch, sternalis, and infraclavicularis muscles; the MPN may innervate the pectoralis quartus, chondrofascialis, axillary arch, chondroepitrochlearis, and sternalis muscles.